The Central Lipid Laboratory will obtain measurements on the National Health and Nutrition Survey (NHANES IV) sample population to accurately measure (a) total cholesterol and HDL cholesterol for the entire NHANES IV sample population and (b) triglycerides for the fasting NHANES IV population, and to deliver the results to NCHS for use in its NHANES IV Survey and to NHLBI for monitoring national trends in cholesterol and other lipid values by comparing the values collected in the NHANES IV with corresponding data gathered in previous surveys. The work of the Central Lipid Laboratory will be conducted in three phases. In Phase I (5.5 months), the Central Lipid Laboratory will measure lipid levels in about 250 samples collected over 1-2 months and prepare a Central Lipid Laboratory manual of operations for the study. In Phase II (6 years) the Central Lipid Laboratory will measure total cholesterol and HDL cholesterol in 22,200 samples with triglyceride measurement in half (11,100) of the samples. In Phase III (4 months) the Central Lipid Laboratory will assay any remaining samples or repeat measurements as required. In addition, the Central Lipid Laboratory will work with NHLBI and NCHS in preparation of journal articles to disseminate the lipid results as well as the national trends.